Lightroom Classic Adjust Camera Preferences

What you show in your screenshots are two different and unrelated things. The first screenshot show the lens profile, the second screenshot shows some issue with creating a camera default. Camera defaults have nothing to do with the lens you use. You should be able to select your camera here, providing that your catalog contains at least one raw image that was shot with this camera. If that is the case and you still can't select the camera, then maybe you should reset the preferences to see if that solves it. Here's how you do this: 

https://www.lightroomqueen.com/how-do-i-reset-lightrooms-preferences/